Acceptance of the human tissue valve for routine cardiac replacement is dependent upon: (1) documentation of its superiority. (2) perfection of those techniques essential for preparation and storage. These are the objectives of our present study. While the trend has been toward perfection of prosthetic devices, it is still clear that the fresh aortic homograft has the longest and most successful clinical record of any valve replacement that has been tried. The aortic valve homograft is a unitized, semilunar graft obtained from the aortic position of the donor. By specialized techniques of preparation, sterilization and storage these grafts can then be used for aortic, mitral or tricuspid replacement. Morphologic studies indicate that if the fresh aortic homograft is used within several days of procurement, donor valve cells persist. Such a graft is a living tissue transplant which can potentially function for an indefinite period. Experiments are being conducted in animal implantation and in vitro tissue culture of these grafts in an effort to evaluate their function and ultimate fate. We are simultaneously carrying on a prospective randomized study which compares the best available prostheses with the fresh aortic homograft.